Several techniques are conventionally known for performing various types of processing on raster data in advance in the case of recording an image with a method such as an inkjet method or an electrophotographic method. For example, the background art section of Japanese Patent Application Laid-Open No. 2003-219171 (Document 1) refers to a technique for correcting a halftone dot area in advance to deal with the phenomenon of dot gain in which halftone dots increase in size as ink spreads. Document 1 discloses a technique for performing thickening or thinning processing by changing densities of edge portions of a halftone dot image to deal with a difference in dot gain between an output device for proofreading and a general printer.
Japanese Patent Application Laid-Open No. 2010-145145, which relates to the field of pattern inspection, discloses that, in the acquisition of a master pattern, a reference pattern that includes a background pattern and a product pattern is used to obtain a reference distance pattern by assigning to each pixel belonging to the product pattern a distance data piece that indicates a distance of the pixel from the boundary. The reference distance pattern is then used to obtain a pixel-deleted image by deleting pixels until each pixel in the reference distance pattern has no surrounding pixels that have greater distance data pieces than that of the pixel. The reference distance pattern is also used to obtain a line-thinned image by deleting pixels until the line width of the reference distance pattern becomes the minimum. The pixel-deleted image and the line-thinned image are then combined to obtain a reference skeleton pattern. The reference skeleton pattern is subjected to inverse distance conversion (i.e., the reference skeleton pattern is thickened) to obtain the master pattern.
Japanese Patent Application Laid-Open No. 2001-301248 discloses a technique for use with a plurality of books that include a fixed part and a variable part and in which the fixed part is shared and only the variable part is rasterized.
Incidentally, in the case of recording superfine characters or line images, converting vector data into raster data (i.e., rasterized) with a raster image processor (RIP) may produce thickened and indistinguishable lines. This is due to the facts that outlined characters have no Hint information to be referenced in the case of recording superfine characters and that pixels representing characters and figures are determined to be writing pixels to prevent superfine parts from becoming broken due to rasterization.